Distributor transmission having at least three shafts

ABSTRACT

A distributor transmission ( 8 ) having at least three shafts ( 11, 12, 13 ) for distributing a drive torque (M_GE) as needed to at least two drive axles ( 4, 5 ). A first shaft ( 11 ) is operatively connected with the first drive axle ( 5 ) and can be loaded with the drive torque (M_GE). The second shaft ( 12 ) is operatively connected with the second drive axle ( 4 ) and a torque (M_E) of a machine device ( 14 ) on a third shaft ( 13 ) can be applied which influences a degree of distribution (P_VA/P_GES) of the drive torque (M_GE) between the drive axles ( 4, 5 ).

[0001] The invention concerns a distributor transmission having at leastthree shafts for distributing a drive torque to at least two drive axlesas needed.

[0002] In power trains of vehicles known from the practice, a drivetorque produced by a prime mover is transmitted via a transmission tothe drive wheels. If vehicles like four-wheel passenger cars orfour-wheel trucks are designed with several driven axles, the power ofthe prime mover in the power drive of such vehicles is distributed tothe individual drive axles and the different drive wheels.

[0003] The specified power distribution is generally carried out withso-called differential transmissions, the longitudinal differentialtransmissions, seen in travel direction, being used for longitudinaldistribution of the input of the prime mover to several driven vehicleaxles. So-called transverse differentials or differential transmissionsare provided in relation to the travel direction of the vehicle for atransverse distribution of the input to the drive wheels of a vehicleaxle.

[0004] The designs of differential transmission, conventional in thepractice, are so-called bevel gear differentials, spur geardifferentials in planetary design, or also worm gear differentials. Spurgear differentials are especially used mostly as longitudinaldifferentials because of the possibility of asymmetric torquedistribution. In the meanwhile, bevel gear differentials constitute thestandard for a transverse compensation in vehicles and worm geardifferentials are used both for longitudinal distribution and fortransverse distribution.

[0005] By means of the longitudinal distributor differentials, a drivetorque can be distributed in arbitrary ratios to several drive axles soas to prevent stresses in a power drive.

[0006] Opposed to this advantage stands the disadvantage that forvariable longitudinal distribution of a drive torque, a longitudinaldistributor differential is designed with a frictional shifting elementor a frictional multi-disc clutch which, during an unequal torquedistribution between two drive axles of a vehicle, are heldsubstantially in a greatly wasteful slip operation whereby aneffectiveness of a power train is sharply reduced.

[0007] Therefore, the problem on which this invention is based is tomake a distributor transmission available by means of a drive torquewhich can be distributed as needed to several drive axles causing onlyminor energy losses in the process.

[0008] This problem is solved according to the invention with adistributor transmission having the features of claim 1.

[0009] With the inventive distributor transmission having at least threeshafts for distributing as needed a drive torque to at least two driveaxles, it is possible to carry out, almost without loss, a variabledistribution of the drive torque between two drive axles.

[0010] This is achieved by the fact that one shaft of the distributortransmission is operatively connected with a machine device by which atorque that influences a degree of distribution of the drive torquebetween the drive axles can be produced upon the shaft almost withoutloss.

[0011] The reduction of the power losses, compared to the longitudinaldistributor transmission known from the practice, results from the factthat input or parts of the drive torque of a prime mover, do not, as wasformerly usual, vaporize as frictional heat in a frictional shiftingelement of a power train, but are applied to the drive axles via thesupport torque applied by the machine device.

[0012] The input of the machine device can be reduced in an adequatemanner, preferably via suitable reduction ratios, between a drive unitof the machine device and the shaft, in a manner such that the lossesoccurring, which correspond to one of the input of the machine deviceduring distribution of the drive torque between the drive axles, aresmall compared to the power losses in a frictional shifting element of alongitudinal distributor transmission known from the practice.

[0013] The inventive distributor transmission has the added advantagethat with it a traction of a vehicle can be substantially improved andspecially a start off in unfavorable operational states is made possiblefor the first time. With the distributor transmission, in the case of adrive axle of a vehicle spinning due to unfavorable road conditions, itis possible, by adequate adjustment of the torque of the machine device,to supply the drive torque to a non-spinning axle. In critical drivingsituations, a torque distribution between several drive axles can beadjusted under control and/or regulation so that a safety in driving canbe easily increased according to the situation compared to conventionaldrive shafts.

[0014] Other advantages and advantageous developments of the inventionresult from the claims and the embodiment described in principle withreference to the drawing. In the drawing:

[0015]FIG. 1 is an extensively schematized representation of a powertrain of a vehicle;

[0016]FIG. 2 is a gear diagram in detailed representation of adistributor transmission of the power train according to FIG. 1; and

[0017]FIG. 3 is a graphic representation of a connection between a powerto be applied by the machine device and a distribution degree of thedrive torque between two drive axles depending on a ratio of afront-axle differential.

[0018]FIG. 1 shows a schematized power train 1 of a four-wheel drivevehicle. The power train 1 comprises one transmission unit or internalcombustion engine 2 and one main transmission 3 which can be any knowntransmission from the practice.

[0019] Between the main transmission 3 and two drive axles 4, 5 of thevehicle, which are connected upon each vehicle side with at least onedrive wheel 6, 7, there is situated a distributor transmission 8 made assummarizing transmission for variable distribution as needed of a drivetorque or of a transmission output torque of the main transmission 3 tothe two drive axles 4 and 5 and thus also to the drive wheels 6 and 7.Between the drive axles 4 and 5 and the distributor transmission 8 isfurther provided one transverse transmission 9, 10 in a design in orderto transmit the part of the drive torque fed respectively to the driveaxles 4 and 5 to the drive wheels 6 and 7 via the drive axles 4 and 5and distribute it between the drive wheels 6 or 7 of a drive axle 4 and5, respectively.

[0020] The distributor transmission 8 has three shafts 11, 12 and 13,the first shaft 11 being operatively connected with the drive axle 5 andit can be loaded with the drive torque or transmission output torque ofthe main transmission 3. The second shaft 12 of the distributortransmission 8 is operatively connected with the drive axle 4 and thethird shaft 13 is connected with a machine device 14 which can beapplied to the third shaft 13 of the distributor transmission; a torquethat influences the degree of distribution of the drive torque betweenthe two drive axles 4 and 5.

[0021] Referring to FIG. 2, it shows an extensively schematized geardiagram of the distributor transmission 8 shown in FIG. 1. In theembodiment of the distributor transmission 8 shown in FIG. 2, thedistributor transmission 8 is designed as a double planetary gear set;it evidently being at the expert's discretion to arrange the distributortransmission 8 with a different adequate design with which the specifiedworking principle can be accomplished.

[0022] A drive torque or a transmission output torque M_GE of the maintransmission 3 (not shown in detail in FIG. 2) is transmitted via acountershaft 15 directly to the drive axle 5 (likewise not shown indetail), which constitutes the rear axle of the vehicle. Besides, thetransmission output torque M_GE is transmitted via a spur gear 16fixedly connected with the countershaft 15 to a ring gear 17 of thedistributor transmission 8. The ring gear 17 is designed as common ringgear for both planetary gear sets 8A and 8B of the double planetary gearset 8 or of the distributor transmission and corresponds to the firstshaft 11 of FIG. 1. With the ring gear 17 mesh planetary gears 18 of theplanetary gear set 8A which are rotatably supported on a planet carrier19. The planet carrier 19 of the planetary gear set 8A is operativelyconnected with a sun gear 20 of the second planetary gear set 8B.

[0023] In addition, with the ring gear 17 mesh planetary gears 21 of theplanetary gear set 8B which are rotatably supported on a planet carrier22 of the planetary gear set 8B which corresponds to the second shaft 12of FIG. 1. The planet carrier 22 of the planetary gear set 8B is, inturn, engaged via a spur gear 23 with a countershaft 24 so that a drivetorque transmitted via the distributor transmission 8 to thecountershaft 24 is passed to the drive axle 4 which constitutes thefront axle of the vehicle.

[0024] The planetary gears 18 of the planetary gear set 8A additionallymesh with a sun gear 25 of the planetary gear set 8A. The sun gear 25 isin operative connection with the machine device 14 designed as anelectric motor in a manner such that when current is supplied to theelectric motor 14, one torque M_E is introduced via the sun gear 25 inthe distributor transmission 8.

[0025] This means that via the electric motor 14, a support torque canbe applied to the sun gear 25 of the planetary gear set 8A depending onwhich the drive torque M_GE, or at least part of the drive torque M_GE,can be transmitted via the distributor transmission 8 to thecountershaft 24 and thus to the drive axle 4.

[0026] Alternative to this it obviously it is also possible that themachine device be designed as a hydraulic machine or as any othermachine with continuously variable drive torque to make adjustingpossible between the two drive axles 4 and 5 an arbitrary distributionof the drive torque M_GE.

[0027] An advantage of the design of the machine device 14 as electricmotor is that an electric motor can be operated both as generator and asmotor. If the electric motor is designed with an intelligent energymanagement, the electric motor can be to a great extent, automaticallyoperated by an electric circuit of a vehicle. It can thus be providedthat the electric motor, when operating as generator, loads an energymemory, for example, a battery or a capacitor, and when operating asmotor, be fed by the energy memory.

[0028] With the design of the distributor transmission 8 (shown in FIG.2), the output of the power train 1 is designed upon the drive axle 5 asrigid and direct through drive from the transmission output of the maintransmission 3 to the drive axle 5. The output on the drive axle 4 ofthe vehicle is realized via the summarizing transmission or thedistributor transmission 8 with the machine device 14. By adequatesetting of a torque produced by the machine device 14, the distributionof the drive torque between the two drive axles 4 and 5 of the vehiclecan be arbitrarily adjusted.

[0029] The transmission output torque M_GE is thus transmitted up to100% to the drive axle 5 when the torque M_E of the machine device iszero since, in this case, there is no support torque on the sun gear 25which would support and transmit at least part of the drive torque M_GEin direction of the drive axle 4.

[0030] If the torque abutting via the machine device 14 on the thirdshaft 13 of the distributor transmission 8, which in the design of thedistributor transmission 8 according to FIG. 2 corresponds to the sungear 25 of the planetary gear set 8A, is boosted or increased, the drivetorque M_GE is increasingly supported and the part of the drive torqueM_GE transmitted in direction of the drive axle 4 increases whereas theportion of the drive torque M_GE transmitted to the drive axle 5diminishes to a great extent.

[0031] Starting from a specific value of the torque M_E of the machinedevice 14, the drive torque M_GE is transmitted up to 100% to the driveaxle 4 via the distributor transmission 8 and the portion of the drivetorque M_GE fed to the drive axle 4 is zero.

[0032] The portion of the drive torque M_GE which is transmitted via thedistributor transmission 8 to the drive axle 4 is directly proportionalto the torque M_E introduced in the distributor transmission 8 via themachine device 14 whereby the expense for control and regulation is low.

[0033] Due to the fact that the distributor transmission 8 is designedas a planetary gear set, the power to be applied by the electric motor14 is low compared to the maximum output power to be transmitted to thedrive axle 4. An electric motor or a machine device 14 with only lowinput is thus required which needs a small installation space. This, inturn, results in that the distributor transmission 8 can be designedwith compact construction and small number of parts.

[0034] The design of the distributor transmission with one machinedevice for variable distribution of a drive torque between two driveaxles gives the additional advantage that an input is substantially lesscompared to a power loss occurring in a slipping clutch of a distributortransmission known from the practice.

[0035] In addition, a power to be applied by the machine device can beinfluenced by the change of a ratio i_VA of the transverse distributortransmission 9 and can preferably be adjusted so that the machine devicedesigned as an electric motor in FIG. 2 can be operated as a generatorand as motor almost with the same portions of time and power.

[0036] This is made clear by the relationship graphically shown in FIG.3 between a power P_E of the electric motor and a distribution degreeP_VA/P_GES of the drive torque M_GE between the two drive axles 4, 5,the distribution degree is reproducing the portion of the drive torquetransmitted via the distributor transmission 8 to the drive axle 4. Thethree curves I, II and III have been determined in tests conducted witha drive torque of 350 Nm, at a vehicle speed of 180 km/h, an input ofthe internal combustion engine of 200 KW and a ratio i_HA of thetransverse distributor transmission 10 with a value of 4.1.

[0037] According to FIG. 3, the three curves I to III are a result ofdifferent ratios i_VA of the transverse distributor transmission 9.Starting from the curve I in direction to the curve III, the ratio i_VAof the transverse distributor transmission 9 was reduced while a totalratio i_GES of the distributor transmission 9 remained constant.

[0038] From the presentation shown in FIG. 3, it results that thedistribution degree of the drive torque between the two drive axles 4and 5 can be continuously adjusted from zero percent to 100% with theelectric motor 14 operating as generator and motor. If the ratio i_VA ofthe transverse distributor transmission 9 of the drive axle 4 isoptimized, the portions of the operation of the electric motor or of themachine device 14 by time unit as generator and as a motor can beadjusted so that the electric motor can be operated as a generator andas motor to similar time units and power portions whereby a powerconsumption of the electric motor can be kept altogether low in themanner specified.

Rerence Numerals

[0039]1 power train

[0040]2 internal combustion engine

[0041]3 main transmission

[0042]4, 5 drive axle

[0043]6, 7 drive wheel

[0044]8 distributor transmission, double planetary gear set

[0045]8A, 8B planetary gear set

[0046]9, 10 transverse distribution transmission

[0047]11, 12, 13 shaft

[0048]14 machine device or electric motor

[0049]15 countershaft

[0050]16 spur gear

[0051]17 ring gear of the planetary gear set 8A

[0052]18 planetary gears of the planetary gear set 8A

[0053]19 planet carrier of the planetary gear set 8A

[0054]20 sun gear of the planetary gear set 8B

[0055]21 planetary gears of the planetary gear set 8B

[0056]22 planet carrier of the planetary gear set 8B

[0057]23 spur gear

[0058]24 countershaft

[0059]25 sun gear of the planetary gear set 8A

[0060] M_E torque of the machine device

[0061] M_GE transmission output torque

[0062] i_GES ratio of the distributor transmission

[0063] i_VA ratio of the transverse distributor transmission 9

[0064] i_HA ratio of the transverse distributor transmission 10

[0065] P_E power of the machine device or electric motor

[0066] P_VA/P_GES degree of distribution of the drive torque

1-10. (CANCELED).
 11. A distributor transmission (8) having at leastthree shafts (11, 12, 13) for distributing a drive torque (M_GE), asneeded, to at least two drive axles (4, 5) in which a first shaft (11)is operatively connected with a first drive axle (5) and can be loadedwith the drive torque (M_GE), a second shaft (12) is operativelyconnected with a second drive axle (4) and on a third shaft (13) can beapplied a second torque (M_E) of a machine device (14) which influencesa degree of distribution (P_VA/P_GES) of the drive torque (M_GE) betweenthe two drive axles (4, 5).
 12. The distributor transmission accordingto claim 11, wherein said three shafts (11, 12, 13) are operativelyinterconnected so that the drive torque (M_GE) without the second torque(M_E) of the machine device (14) is transmitted entirely to said firstdrive axle (5).
 13. The distributor transmission according to claim 12,wherein the drive torque (M_GE) is increasingly transmitted to saidsecond drive axle (4) with rising torque (M_E) of said machine device(14).
 14. The distributor transmission according to claim 11, whereinsaid machine device (14) is designed as an electric motor, which can beoperated as a generator and as a motor.
 15. The distributor transmissionaccording to claim 11, wherein said distributor transmission (8) has atleast one planetary gear set.
 16. The distributor transmission accordingto claim 15, wherein said first shaft (11) is a ring gear (17).
 17. Thedistributor transmission according to claim 15, wherein said secondshaft (12) is a planet carrier (22).
 18. The distributor transmissionaccording to claim 15, wherein said third shaft (13) is a sun gear (25).19. The distributor transmission according to claim 11, wherein betweensaid two drive axles (4, 5) and said first and second shafts (11, 12)operatively connected therewith at least one transverse distributortransmission (9, 10) is situated.
 20. The distributor transmissionaccording to claim 14, wherein a ratio (i_VA) of said transversedistributor transmission (9) of said second drive axle (4)